2 Chronicles 36:21

21 The land enjoyed its sabbath rests; all the time of its desolation it rested, until the seventy years were completed in fulfillment of the word of the LORD spoken by Jeremiah.

Read 2 Chronicles 36:21 Using Other Translations

To fulfil the word of the LORD by the mouth of Jeremiah, until the land had enjoyed her sabbaths: for as long as she lay desolate she kept sabbath, to fulfil threescore and ten years.
to fulfill the word of the LORD by the mouth of Jeremiah, until the land had enjoyed its Sabbaths. All the days that it lay desolate it kept Sabbath, to fulfill seventy years.
So the message of the LORD spoken through Jeremiah was fulfilled. The land finally enjoyed its Sabbath rest, lying desolate until the seventy years were fulfilled, just as the prophet had said.